Thomas sheehan



T. SHEEHAN.-

Making Filesand Rasps.

Patented Feb. 5, 1861.

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lTHOHAS SI-IEEI-IAN, OF DUNKIRK, NEIV YORK, ASSIGNOI-t 'IO I-IIMSELF, AND C. D. SMITH AND CHAS. B. MOSS, OF 'ASHINGTON, DISTRICT OF COLUMBIA.

MANUFACTURE OF FILES AND RASPS.

Specification of Letters Patent No. 31,331, dated February 5, 1861.

To LZ2 whom it may concern:

Be it known that I, THOMAS SHEEHAN, of Dunkirk, in the county of Chautauqua, in the State of New York, have invented certain new and useful Improvements on Files and Rasps; and I do hereby declare that the following is a full and exact description of my invention and of the manner and process of making the same, reference being had to the annexed drawings, making a part of this specification.

Files whether intended,-according to their several kinds,-for filing the hard or soft metals, or for heavy or for light work, as also rasps,-have hitherto been made wholly of steelthose of cast-steel, although of a higher price, being preferred, because of their excellence in hardness and durability. men, however, that a file so made, no matter of what kind of steel, is easily broken by a blow of a certain force, by a pressure more or less severe, or by falling on a hard body; and thus becomes worthless as a tool, and valueless save as old metal. It is true that some iiles,'such for instance as certain of' the files used by sculptors and diesinkers` have been made wholly of iron. case-lmrdened; and that they could be bent intoany desired curve without annealing, or drawing the temper as this process is sometimes called1 acquiring a superficial hardness, by the case-hardening sufficient for filing the comparatively soft substances on which they were to be used. But the broad inference, however, which has been too carelessly drawn from the limited filing capacity of these peculiar files, viz-that files made in this way, are sufficiently hard to answer the purpose of any file, is not, and

cannot, from the very nature of a merely case-hardened surface, be true; and the fact, that the various sorts of files used generally for filing the metals, whether hard or soft, in heavy or light work, have never been so manufactured or used as substitutes for cast steel files, and are not to be found anywhere in market as vendible articles of merchandise, and as such substitutes, proves not only that they are not hard and durable enough for the work for which cast steel tiles are used; but that this inference is a gratuitous generalization.

It is a fact familiar to work-l Now my invention consists in making files and rasps in such a manner, that they shall be equal, at least, in hardness, working qualities, and durability to cast steel files and rasps; and hence my improved files and rasps can be substituted for those of cast steel, and at a much less cost. The mode by which my said invention is carried into effect comprehends the following processes. First, the making of the files and rasps wholly of wrought or malleable iron. Second, instead of giving to these iiles and rasps al superficial hardness by simple case hardening, the converting of the iron of these files, ttc., into a. sound and very tenacious steel, for a certain and uniform depth, by coating the files and rasps with a proper cementing paste, then packing` them with ground bones and scrap leather in a wrought iron box, which is afterward tightly closed, and finally submitting the whole to the action of heat till this partial conversion into steel is effected. Third, the hardening and cleaning of these now steelified wrought iron files and rasps (for such they may be called, in view of these processes) which fits them for immediate use. But this mode of manufacturing them requires a careful attention to the following details. Vith regard to the making of the files, I have found that Swedish iron does not answer so well; for with the same thickness of cementit is too deeply converted in the same time, not leavingA a sufficient body or core of malleable iron, and hence the files made of such iron are as frangible as steel files. It may however be used if care be taken to ascertain the correct Quantity of cement.

The kind of iron that I have found to be most suitable for the purpose, and to which my converting process has been specially adapted, is American, Russian, or common English or low-moor wrought or malleable iron, carel being taken to select that which is solid, and free from scale, fiaws, seams and other defects. From iron of this kind and quality the file-blanks of the various sizes, proportions and shapes required are forged in the usual manner; but it may be remarked, they could be formed much more rapidly and economically by pressure properly directed by means of machinery easily contrived for the purpose. The blanks, however made, are then finished, by clear ing their surfaces of all foreign matters, working them accurately even and smooth, by grinding or filing or by both, and nally formed` into tiles by toothing these dressed surfaces of the desired neness or coarseness, either by hand or machine.

The depth to which the iron of the files are converted into steel of the character above described, exclusive of the teeth, will depend both upon the length and the fineness or coarseness of the cut of the particular kind of tile. For roughs and bastards of the smaller sizes, say from four to eight inches long, the steel, below the teeth, should not be less than one-sixty-fourth, n'or greater than one-thirty-second part of an inch deep; while for those of from twelve to twentyone inches long, the depth should be at least one thirty-second, but not greater than onesixteenth of an inch. For smooth iles, this depth of steel should be one sixty-fourth of an inch for the smaller sizes, and not more than one-thirty-second for the larger; while for the yvery thin' smooth files used for watch-making and some other purposes, the depth may be much less than one sixtyfourth part of an inch. It may be re marked, however, that my working tests show, that a depth of steel, below the teeth, of one sixty-fourth of an inch will be amply sufficient for the larger, as well as the smaller files of either cut; but it would not be )rudent to carry it beyond one-sixteenth o "an inch, as from the consequent development of brittleness, and the high temper given to the steel, it would crack when bent or sub-f jected to concussion.

The wrought iron box in which the files are packed should have a thickness of metal sullicient to give it a strength proportionate to the size and weight of the tiles. Its cover of the same metal, provided with a venthole to allow the free escape of gas and vapor, should be made to tit close. The box ought to be of such dimensions internally, as to contain a dozen coated tiles and the necessary packing of bone and leather, the length being half an inch greater than that of the files, while the breadth is a half inch and the depth is one inch greater respectively than the similar dimensions of the coated files and -the packing of the same width and length of coarser tiles. The packing of scrap leather and ground bones is made by intimately and uniformly mixing two parts by weight of the former, with one part by weight of the latter ingredient; but this proportion, too, may be varied according rto the kind of leather.

The cementing paste with which I coat the tiles is Sheehans compound for steelifying wrought iron, the manner and process of making which is fully described in the specification annexed to the patent granted to me by the United States on the fourth dayof September, in the year one thousand eight hundred and sixty, and recorded inA the Patent Office; but it may be briefly stated in this place that the compound consists of a paste formed of a liquid co1nposition,-also fully described in said speciications,and flour; and can be made of any desired consistency, by properly proport-ioning these ingredients.

Vith regard to the thickness of coating actually necessary for the conversion of the iron to the proper depth; it should evidently be proportionate to such depth; and as a coat of the compound one-fourth of an inch thick is quite sufficient to give. a depth of steel proper for the thickest and coarsest tile; the thickness of coat necessary to give that for a thinner, is easily deducible. lt is quite unnecessary however to reduce this thickness below one-fourth of an inch, as by my process, the thinner tiles having a coating of this thickness, consume no more of the compound than is just sutlicient to give them the proper depth of steel at the moment they have attained a temperature proper for hardening; when the process of conversion is of course stopped. It is true that there is a loss of compound, thus inf curred by not proportioning the thickness of coating for less depths of steel; but my experience shows that it is more than compensated by the saving of the time and labor required by such an operation. Hence, my general rule for coating files, and which has liever' failed to give ra proper depth of steel, within the limits before stated, is first to mix the compound of such a consistency that the quantity adhering to the thickest and coarsest lfile thoroughly dipped in it, will be such as to form, when evenly spread along the file, a coating one-fourth of an inch uniformly thick; and then to dip the tiles to be coated, whether they be thick or thin, until they have taken up as much of this compound as will adhere to them, spreading the same evenly over the files, so as to form coatings uniformly thick. It may be remarked, too, that the relative weights of flour and liquid composition required for this consistence, being now determined, I am enabled to form, at any other time and without trials,'a compound of the same consistenee. A, dozen wrought iron files having been coated in this manner, and an iron cementation-box, properly proportioned to the size and number of the files, provided,- the process of cementation is thus managed: Over the bottom of the box, a layer of the mixed bones and leather half an inch deep is evenly and compactly spread; and on this, four of the coated files are carefully laid fiat, a quarter of an inch apart, thus leaving the same space between them and the sides and ends of the box. Mixed bones and leather are now poured into the box and spread evenly, till a uniform layer, half an inch deep, is formed above the coated files, on which layer four more of the coated files are laid, in the same manner as at first. Bones and leather are again spread in the box till another layer of this mixture half an inch deep is formed, on which the last four of the coated files are arranged as before. The remaining space in the box is filled with bones and leather; and if the box has been properly proportioned, this last layer will be one inch deep. The charge of the box will then consist of three layers, of four coated files each, alternated with four layers of mixed bones and leather; and is much better arranged for the reception and distribution of heat than if the box had been of such dimensions as to have made it necessary to alternate four layers of three files each, with five layers of bones and leather. And herev it must be stated, that l never make the boxes of a capacity greater than what is just sufficient for one dozen coated files or rasps, with the requisite quantity of bones and leather, for the files, &e., from their limited number, besides being more uniformly heated and converted, are hardened equally and uniformly with much more certainty, than if the number were greater, the time between their removal from the re and the completion of the hardening process being too short to admit of an injurious loss of temperature. Figure G, will give a general idea of this mode of charging the box.

If there is any cause to apprehend, as from the weight of the files, that the under coatings willv be pressed out laterally, it will be well to cover with very finely shredded leather, the surface of each layer of bones and leather on which the files are to be arranged, in such a way that the shreds may cross each other, for when the files are carefully let down on this, the compound will be pressed into its meshes or reticulations, and, thus prevented from spreading, will be kept under the files so as to act with all its effi mcy. Another mode, and perhaps a better one, to effect the same object, is to dry the coating' on the files byI gentle evaporation in a varm room, till it becomes compact enough to resist displacement when the files are placed in the box. Very light files will notprobably need this precaution, particularly if the leather be cut up as small as before directed. In all eases, however, care should be taken to cover with compound such parts ofthe files as have been left bare by handling. Having somewhat freely sprinkled the top layer of bones and leather with the liquid composition so as to settle it down on the files, but not so much so as to soften the coating which may have been dried to prevent displacement, the lid is now placed on the box so as to fit close; and the seams of the `joint luted with a mixture of equal parts of sand and clay. The box thus charged is then placed in the open fire of a. common smiths forge in such a manner, that the heat and fiame may circulate freely under as well as around and over it; the vent in the 'lid being covered with live coals or loosely with a piece of plate iron, so as to protect its contents from the ingress of flame and air, and yet to allow the escape of gas or vapor.

The fuel to be used is good dry fire-wood, and with this the re should be freely and regularly supplied, in order to keep up a sufficient heat, the blast being used at first to raise the fire to the proper intensity, but after that only let on occasionally to maintain it uniformly at that point. The files must now be brought to a bright cherry red heat gradually, as a quick, intense fire will infallibly blister and scale them; and when this heat is attained, the conversion to the necessary depth is completed. Great care, however, must be taken that the fire be so managed that all the files shall be of this temperature when the operation is finished, so that they be susceptible of the same degree of hardness.

The hardening bath is made by adding one gallon of table salt to every six gallons of water, rain or other soft water being preferable, and by some means that will not dilute it, should always be kept at the same temperature during the hardening of the files. The moment that the files have attained the bright cherry red heat, which may be ascertained by simply lifting the lid, the box is removed to the bath. Commencing with the top layer, each file is successively taken out by its tang or shank without exposing theother files to the action of air, plunged rapidly and perpendieularly into the bath, briskly moved around in the fluid so as to be quickly and uniformly hardened, and then left in the vessel till all the files have undergone the same treatment. After this the files are immediately transferred to a bath of the strongest lime water in which they are allowed to remain some twelve or fourteen hours; and at the expiration of this time they are taken out, straightened, if necessary, in the manner before explained, and then scrubbed with fine sand and water 40 f f particularly for operating on the large scale,

till they are perfectly clean. They are next severally held over the blaze of a clear fire, passed to and fro till they become too hot to be retained by the hand, and then well brushed with a mixture of equal parts of lard-oil and spirits of turpentine, leaving them slightly moistened all over. Finally they are wrapped in strong brown paper, and laid up for use or the market. The rasps are manufactured in the same way.

When the liquid composition is deficient in strength, the iron inferior in quality for its kind, or the firing has been mismanaged, the depth 0f steel may be less than what is desirable, and this is easily ascertainable from a coated test piece of the same kind and thickness of wrought iron as those of the files with which it has been converted. In such a case, the files may be 'recoated or not according to the quantity of compound left on them; and may again be submitted to the converting process, till they have received a sutlicient depth of steel.

I have preferred fire-wood as a fuel because charcoal, coke and the mineral coals rapidly destroy the iron converting box, which should serve for several operations. However', when it is desirable from any cause to use the other fuels, the difliculty may be removed by coating the box with clay or any other suitable fire lute. Nor is the smiths forge to be considered as the preferable source of heat any further, than as it is the more simple and common one; for if the gradual bringing of the files to a bright cherry red. heat, and the other necessary conditions for the proper manage-y ment of the fire, can be carried 0ut,-1n using any other, a cementation oven, or a furnace of suitable form would answer the purpose,

rwhen the number of boxes of tiles to be conall of which is verilied by the testimony of 'Y machinists which has been filed in the U. S. Patent Olice with this specification. They will moreover possess, besides these valuable qualities, two other recommendations, viz., that they can be manufactured, particularly by this method, at about one half the cost of cast steel files'&c., and that when their teeth are worn out, they can be stripped, dressed, cut, converted and hardened, the same as their blanks were at first.

Having thus fully described my invention, and a method by which it can be practiced, I disclaim having invented certain filesused by sculptors and die-sinkers made of wroughtl iron simply case hardened, but

Iliat I do claim as of my own invention, and what I desire to secure by Letters Patent, as new, useful and improved manufactures are- Non-frangible files and rasps, constructed and made as hereinbefore described and specified, whose hardness, Working quali! rties,-and` durability are equal to those 0f caststeel files and rasps. f

THOMAS .SI-IEEHAN` IVitnesses:

Trios NARPLET, IVM. H. GooDs. 

